A block chain is a distributed database that includes and maintains an ever growing list of data records. Being distributed, the block chain is effectively tamper and revision proof. There are many applications for a block chain, including the public ledgers of transactions for cryptocurrencies, such as bitcoin, name-coin, and so on. For example, the block chain enables decentralized digital currencies, because bitcoin transactions are verified by network nodes (e.g., addresses), and recorded in the public, distributed ledgers.